Saxifragaceae

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The familial limits of the Saxifragaceae family have long been uncertain, mostly due to a morphologically more or less intermediate position in traditional classification schemes. Molecular studies have considerably improved our understanding of the family (Morgan & Soltis 1993; Soltis & al. 1993, 2001). Many genera are now accommodated in other families, the woody and shrubby ones in e.g. Hydrangeaceae (e.g. Deutzia, Hydrangea, Philadelphus), Grossulariaceae (e.g. Ribes) or Escalloniaceae (e.g. Escallonia), others in e.g. Parnassiaceae (Celastraceae s.l.). The remaining genera form a firm clade that clearly falls apart in two major groups: the genus Saxifraga (that is polyphyletic in its traditional circumscription) and the so-called heucheroid-clade that encompasses all other genera.

At present Saxifragaceae counts ca. 38 genera and ca. 600 species (Soltis 2007, Fortson Wells & Elvander 2009). Only two genera are native to Belgium, Chrysosplenium and Saxifraga (Lambinon & Verloove 2012). In addition to the genera included in this account, another one has also been encountered in Belgium: Astilbe. Assessing the identity of these plants, however, requires further study. Moreover, in most cases it seems to be nothing else than a mere relic of cultivation.

8 Rhizomatous perennial, rhizomes stout and scale. Leaves large and thick, the larger at least 10 cm across. Petals pink or red, never white === Bergenia
Annual to perennial (sometimes stoloniferous but usually not rhizomatous or rhizomes short and thin). Leaves usually much smaller. Petals white, sometimes yellow or pink/red (only in cultivars) === Saxifraga